For the most part, yes. The “style” is basically the same, just with a different color palette. The presentation or packaging, however, is different. The Nine Realms stuff has been made so far to be plugnplay w/ RPGmaker MV/MZ, so the way spritesheets are arranged is set up for that. The Retro Cybercity packs are more general-purpose with spritesheets that you are more likely to have to slice a little if you’re using specific engines or software.
Does that make sense? The answer is pretty much yes, but you may need to do a little rearranging on the sheets. If you don’t know how to do that, I can help you out.